Method and apparatus to supply power voltage to a mobile device in a variable manner

ABSTRACT

A method and apparatus to supply a power voltage to a mobile device in a variable manner in order to provide high output power and a high quality sound environment and a mobile device using the same. The apparatus includes a volume control unit to detect installation of an external power supply and to generate a voltage control value corresponding to a current volume level, and a DC-DC converter unit to convert a voltage of an internal power supply in a variable manner on the basis of the voltage control value generated in the volume control unit in order to drive the switching power amplifier.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 11/651,016 filed Jan. 9, 2007 in the U.S. Patent and TrademarkOffice, which claims the benefit of Korean Patent Application No.10-2006-0060685, filed on Jun. 30, 2006, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present general inventive concept relates to a mobile device, andmore particularly, to an apparatus and method of supplying separatepower voltage to a switching power amplifier stage in a variable mannerin order to provide high output power and a high quality soundenvironment, and a mobile device using the same.

2. Description of the Related Art

Typically, mobile devices are internally provided with a D-classswitching power amplifier and a loud speaker to play back audio signals.In the D-class amplifier, the audio signal changes into a pulse widthmodulation (PWM) signal in order to perform a switching operation. Also,the mobile devices adopt an external power supply unit such as a cradleand a secondary battery which is rechargeable.

A technology relating to a mobile device that uses a conventionalexternal power supply unit illustrated in FIG. 1 is disclosed inJapanese Patent Document No. 2004-112377, entitled “Portable InformationTerminal”, filed in Sep. 19, 1992.

Referring to FIG. 1, the portable information terminal uses a powervoltage supplied from an internal battery B to drive a D-class amplifier18 when a power voltage is supplied from an external power supply 36.The D-class amplifier 18 is driven by a low voltage from the battery B.

In contrast, the portable information terminal cuts off the batteryvoltage being supplied to the D-class amplifier 180 and supplies a highexternal voltage to the D-class amplifier 18 when the power voltage isnot supplied from the external power supply 36. Accordingly, the D-classamplifier 18 is driven by a high voltage from an external power supply360 (not illustrated).

Generally, the external power voltage for charging the battery B has alevel relatively higher than the voltage of the battery B inconsideration of safety. Therefore, the conventional portableinformation terminal may output an abrupt loud sound when the higherlevel voltage is supplied, and a user's hearing may be damagedaccordingly. In addition, the power supply unit of the portableinformation terminal of FIG. 1 is susceptible to noises and cannotguarantee safety. Furthermore, although the conventional portableinformation terminal is provided with an internal loud speaker, theinternal loud speaker cannot be driven by a high output power due to itsstructural characteristic.

SUMMARY OF THE INVENTION

The present general inventive concept provides an apparatus to supply apower voltage to a mobile device in a variable manner, in which aseparate power voltage to drive a switching power amplifier is suppliedin a variable manner, and a volume can be adaptively controlled by aboosted voltage when an external power supply is installed, so that asignal to noise (S/N) ratio can be improved.

The present general inventive concept also provides a method ofsupplying a power voltage to a mobile device in a variable manner.

The present general inventive concept also provides a mobile deviceusing the method and apparatus to supply a power voltage in a variablemanner.

Additional aspects and utilities of the present general inventiveconcept will be set forth in part in the description which follows and,in part, will be obvious from the description, or may be learned bypractice of the general inventive concept.

The foregoing and/or other aspects and utilities of the present generalinventive concept may be achieved by providing an apparatus to supply apower voltage to a mobile device that has a switching power amplifier ina variable manner, the apparatus including a volume control unit todetect an installation of an external power supply and to generate avoltage control value that corresponds to a current volume value, and aDC-DC converter unit to convert a voltage of an internal power supplyinto a DC-DC voltage in a variable manner on the basis of the voltagecontrol value which is generated in the volume control unit to controlan output level of the switching power amplifier.

The foregoing and/or other aspects and utilities of the present generalinventive concept may also be achieved by providing a method ofsupplying a power voltage to a mobile device in a variable manner,wherein the method includes modulating a digital audio signal into apulse width modulation (PWM) signal, detecting an installation of anexternal power supply, reading a volume value when it is detected thatthe external power supply is connected, generating a voltage controlvalue that corresponds to the volume value by comparing the volume valuewith a reference value, performing a DC-DC conversion in a variablemanner for a voltage supplied from an internal power supply unit on thebasis of the generated voltage control value, and performing powerswitching on the PWM signal on the basis of the voltage control value tocontrol a signal output.

The foregoing and/or other aspects and utilities of the present generalinventive concept may also be achieved by providing a mobile deviceincluding a microcomputer unit to generate a volume value thatcorresponds to a volume setting, a pulse with modulation (PWM) unit tomodulate a digital audio signal into a PWM signal that has a smalloutput level, a variable power supply unit to detect an installation ofan external power supply and to convert a voltage of an internal powersupply into a DC-DC voltage in a variable manner on the basis of avoltage control value that corresponds to the volume value generated inthe microcomputer unit, and a power switching circuit unit to performswitching power amplification on a PWM signal which is generated in thepulse width modulation unit based on a voltage output from the variablepower supply unit.

The foregoing and/or other aspects and utilities of the present generalinventive concept may also be achieved by providing an apparatus tosupply a power voltage to a mobile device in a variable manner, theapparatus including a microcomputer to read a volume level, an internalpower supply unit to generate and output an internal power voltage, anda DC-DC converter unit to receive and amplify the internal power voltageto a voltage corresponding to the volume level as the volume levelincreases above a predetermined threshold.

The foregoing and/or other aspects and utilities of the present generalinventive concept may also be achieved by providing an apparatus tosupply a power voltage to a mobile device in a variable manner, theapparatus including a volume control unit to generate a control voltagevalue corresponding to a volume value when an external power supply isdetected and the volume value is greater than a predetermined threshold,and a DC-DC converter unit to amplify an internal power voltage to avoltage corresponding to the voltage control value to control an outputlevel of the switching power amplifier.

The foregoing and/or other aspects and utilities of the present generalinventive concept may also be achieved by providing an apparatus tosupply a power voltage to a mobile device in a variable manner, theapparatus including a pulse width modulator to modulate a digital audiosignal into a pulse width modulation (PWM) signal, a sensor to detectwhether an external power supply is installed, a microcomputer to read avolume value when the external power supply is detected, a volumecontrol unit to generate a voltage control value corresponding to theread volume value by comparing the read volume value with a referencevalue, a DC-DC converter unit to perform a DC-DC conversion in avariable manner for a voltage supplied from an internal power supplyunit on the basis of the generated voltage control value, and a powerswitching unit to perform power switching on the PWM signal on the basisof the generated voltage control value to control a signal output.

The foregoing and/or other aspects and utilities of the present generalinventive concept may also be achieved by providing an apparatus tosupply a power voltage to a mobile device in a variable manner, theapparatus including a sensor to detect whether or not an external powersupply is installed, a digital volume controller to control a volume ofthe mobile device when the external device is not installed, and avariable power supply unit to generate a voltage control valuecorresponding to a volume value by comparing the volume value with areference value, and to perform a DC-DC conversion in a variable mannerfor a voltage supplied from an internal power supply unit on the basisof the generated voltage control value when the external device isinstalled.

The foregoing and/or other aspects and utilities of the present generalinventive concept may also be achieved by providing a method ofsupplying a power voltage to a mobile device in a variable manner,wherein the method includes reading a volume level, generating aninternal power voltage, and amplifying the internal power voltage to avoltage corresponding to the volume level as the volume level increasesabove a predetermined threshold.

The foregoing and/or other aspects and utilities of the present generalinventive concept may also be achieved by providing a method ofsupplying a power voltage to a mobile device in a variable manner,wherein the method includes generating a control voltage valuecorresponding to a volume value when an external power supply isdetected and the volume value is greater than a predetermined threshold,and amplifying an internal power voltage to a voltage corresponding tothe voltage control value to control an output level of the switchingpower amplifier.

The foregoing and/or other aspects and utilities of the present generalinventive concept may also be achieved by providing a method ofsupplying a power voltage to a mobile device in a variable manner,wherein the method includes supplying a voltage from a power supply,reading a volume value, comparing the read volume value to a referencevalue, controlling a volume of the mobile device using an existingdigital volume control and setting the voltage of the power supply to aminimum value if the volume value is smaller than the reference value,supplying a voltage control value corresponding to the volume value to aDC-DC converter unit if the volume value is higher than the referencevalue, and outputting a voltage corresponding to the voltage controlvalue to an amplifier.

The foregoing and/or other aspects and utilities of the present generalinventive concept may also be achieved by providing a method ofsupplying a power voltage to a mobile device in a variable manner,wherein the method includes detecting whether an external power supplyis installed, controlling a volume of the mobile device when theexternal device is not installed, and generating a voltage control valuecorresponding to a volume value by comparing the volume value with areference value, and to perform a DC-DC conversion in a variable mannerfor a voltage supplied from an internal power supply unit on the basisof the generated voltage control value when the external device isinstalled.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and utilities of the present generalinventive concept will become apparent and more readily appreciated fromthe following description of the embodiments, taken in conjunction withthe accompanying drawings of which:

FIG. 1 is a block diagram illustrating a mobile device that has aconventional external power supply;

FIG. 2 is a block diagram illustrating a mobile device that is driven bya variable power supply unit according to an embodiment of the presentgeneral inventive concept;

FIG. 3 is a detailed view illustrating an exemplary embodiment of thevariable power supply unit illustrated in FIG. 2;

FIG. 4 is a flowchart illustrating operations of the volume control unitillustrated in FIG. 3;

FIG. 5 is a graph illustrating a method of setting a target voltage in avolume control unit according to an embodiment of the present generalinventive concept;

FIG. 6 is a circuit diagram illustrating a switching circuit unit and alow pass filter (LPF) unit according to an embodiment of the presentgeneral inventive concept; and

FIG. 7 is a waveform chart of a PWM signal that is output from aswitching signal unit according to an embodiment of the present generalinventive concept.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the embodiments of the presentgeneral inventive concept, examples of which are illustrated in theaccompanying drawings, wherein like reference numerals refer to the likeelements throughout. The embodiments are described below in order toexplain the present general inventive concept by referring to thefigures.

FIG. 2 is a block diagram illustrating a mobile device driven by avariable power supply according to an embodiment of the present generalinventive concept.

The mobile device of FIG. 2 includes a digital signal processing (DSP)unit 210, a microcomputer (MICOM) unit 220, a pulse width modulation(PWM) unit 230, a power switching circuit unit 250, a variable powersupply unit 240, a low pass filter (LPF) unit 260, and a loud speakerunit 270.

When a volume value is input from a remote control or the like, theMICOM unit 220 converts the volume value into volume level informationand a volume control signal. In this case, the MICOM unit 220 outputsthe volume control signal to the DSP unit 210 according to the volumevalue, and also outputs the volume value to the variable power supplyunit 240.

The DSP unit 210 transforms the audio signal input thereto, according toan operation control signal of the MICOM unit 220, into pulse codemodulation (PCM) audio data and performs signal processing operations,such as equalization and enhancement. Particularly, the DSP unit 210controls a gain of an input digital audio signal according to the volumecontrol signal generated in the MICOM unit 220 when an external powersupply, such as a battery charger, is not provided.

The PWM unit 230 compares levels of a carrier signal and a PCM signaloutput from the DSP unit 210 so as to generate a pulse width modulation(PWM) signal that has a low voltage level.

The variable power supply unit 240 generates an internal power voltagefrom a secondary battery to supply the power voltage to each circuitblock when an external power supply, such as a battery charger, isremoved. Also, the variable power supply unit 240 generates a voltagecontrol value corresponding to the volume value input from the MICOMunit 220 when an installation of the external power supply is detected,and supplies a variable target voltage to the power switching circuitunit 250 according to the voltage control value using a DC-DC converter,which is separately provided.

The power switching circuit unit 250 amplifies a small output PWMsignal, which is generated in the PWM unit 230, into a large output PWMsignal according to a variable voltage supplied from the variable powersupply unit 240. For example, the power switching circuit unit 250amplifies a small output PWM signal that has a voltage level of 3.3 Vinto a large output PWM signal that has a voltage level of 5 to 40 V.Particularly, the power switching circuit unit 250 may amplify theoutput from the PWM unit 230 using a voltage supplied from a DC-DCconverter separately provided in the variable power supply unit 240.

The LPF unit 260 removes noises from the PWM signal, the power of whichhas been amplified by the power switching circuit unit 250, by low passfiltering so as to extract an original audio signal.

The loud speaker unit 270 reproduces the audio signal extracted in theLPF unit 260.

FIG. 3 is a detailed view illustrating an exemplary embodiment of thevariable power supply unit 240 illustrated in FIG. 2.

The variable power supply unit 240 illustrated in FIG. 3 includes anexternal power supply unit 310, an internal power supply unit 320, avolume control unit 330, and a DC-DC converter unit 340.

The external power supply unit 310 supplies external power using abattery charger or a cradle.

The internal power supply unit 320 is an internal battery which may beconstructed of a secondary battery which is rechargeable by using thepower voltage supplied from the external power supply unit 310. Theinternal power supply unit 320 separately supplies a voltage to eachcircuit block and the DC-DC converter unit 340.

The volume control unit 330 detects an installation of the externalpower supply unit 310 and then generates a voltage control valuecorresponding to a current volume value if it is detected that theexternal power supply unit 310 is installed. For example, the volumecontrol unit 330 reads volume information currently generated in theMICOM unit 220 of FIG. 2 if the external power supply unit 310 isinstalled. If the read volume value is higher than a reference value,the volume control unit 330 generates a volume control valuecorresponding to the volume value and applies it to the DC-DC converterunit 340. Otherwise, the volume control unit 330 issues a volume controlcommand to the MICOM unit 220 in order to use an existing volume controlmethod.

The DC-DC converter unit 340 converts a voltage supplied from theinternal power supply unit 320 into a voltage corresponding to a currentvolume level according to the voltage control value generated in thevolume control unit 330 in a variable manner. The DC-DC converter unit340 supplies the converted voltage to the power switching circuit unit250 of FIG. 2. As a result, the power switching circuit unit 250performs power switching according to the boosted voltage supplied fromthe DC-DC converter unit 340 instead of the voltage supplied from theinternal power supply unit 320.

FIG. 4 is a flowchart illustrating operations of the volume control unit330 illustrated in FIG. 3.

In operation 420, it is detected whether the external power supply unitsuch as a battery charger or a cradle, is installed by using apredetermined sensor. The predetermined sensor may be a typical on/offswitch or an installation sensor. When it is determined that theexternal power supply is not installed, a command to control the volumeusing an existing digital volume control is generated.

In contrast, when it is determined that the external power supply isinstalled, the volume value which is currently set is read from thevolume information in operation 430.

In operation 440, the current volume value is compared with thereference value. Accordingly, the reference value is set as a volumevalue capable of reproducing the audio signal without amplificationusing the DC-DC converter unit 340 of FIG. 3.

If the current volume value is smaller than the reference value, acommand to control the volume using the existing digital volume controlis generated in operation 460. Accordingly, the voltage of the powersupply unit is set to a minimum value within an allowed range in orderto minimize sound quality degradation caused by power noises.

In contrast, if the current volume value is higher than the referencevalue, the output level cannot be sufficiently driven by only thevoltage from the internal power supply unit 320 of FIG. 3 as the volumevalue increases. Therefore, a voltage control value corresponding to thevolume value is supplied to the DC-DC converter unit 340 in operation450. The DC-DC converter unit 340 outputs the boosted voltagecorresponding to the voltage control value to the power switchingcircuit unit 250 of FIG. 2 to allow the output to be controlled.

FIG. 5 is a graph illustrating a method of setting a target voltageusing the volume control unit 330 of FIG. 3, according to an embodimentof the present general inventive concept.

Referring to FIG. 5, the reference numeral 510 denotes a volume curvethat uses conventional digital volume control processing, the referencenumeral 520 denotes a level of a target voltage V_(T) supplied from thebattery to the power switching circuit, and the reference numeral 530denotes a volume curve that is changed by the DC-DC converter unit 340of FIG. 3 when a battery charger is installed.

As illustrated in a line 520 of the graph of FIG. 5, a voltage V_(T) issupplied to the power switching circuit unit 250 of FIG. 2 from only theinternal power supply unit 320 of FIG. 3 when the current cannot besufficiently applied (for example, when the battery charger is notinstalled). This voltage level is supposed to be 0 dB. In this case, thevolume control is performed by only the conventional digital volumecontrol processing as illustrated in a line 510 of the graph.

In addition, when the current can be sufficiently applied (for example,when the battery charger is installed), the voltage level can beincreased by the DC-DC converter unit 340 up until a desired outputlevel of the PWM signal is obtained. This voltage level is expressed asX dB. In this case, the volume level is increased as high as X dB incomparison with the region 510 that can be controlled by only theconventional digital volume. In addition, since the power switchingcircuit unit 250 is driven by only the voltage boosted by the DC-DCconverter unit 340, the output of the PWM signal can be increased ashigh as the boosted voltage without a change of current or impedance ofthe loud speaker unit 270 of FIG. 2. Furthermore, if the output of thesignal is increased over a predetermined level, a listener becomesrelatively more sensitive to the power noise which is output togetherwith the sound signal. Therefore, the power switching circuit unit 250is driven by a low voltage using an internal battery during a portablestate, and is driven by an external high voltage when the batterycharger is installed, thereby increasing a maximum output level.

FIG. 6 is a circuit diagram illustrating the power switching circuitunit 250 of FIG. 2 and the LPF unit 260 of FIG. 2, according to anembodiment of the present general inventive concept.

The power switching circuit unit 250 can include a PMOS transistor P1and an NMOS transistor N1. A PWM signal is divided into a first PWMsignal Q1 and a second PWM signal Q2 that have the same phase. Powerswitching of the PMOS transistor P1 is performed depending on the firstPWM signal Q1, so that an actual voltage Vcc2 is supplied to its source.The power switching of the NMOS transistor N1 is performed depending onthe second PWM signal Q2, so that its drain is connected to a drain ofthe PMOS transistor P1, and its source is connected to a ground voltageVss2. In this case, a voltage Vcc1 is supplied from the DC-DC converterunit 340, and the voltages Vcc2 and Vss2 are dropped to a predeterminedvalue by resistors R1 and R2, respectively in a wire line 50, whichinterconnects between the voltage source and the power switching circuitunit 250, and correspond to an actual voltage supplied to the powerswitching circuit unit 250.

The LPF unit 260 includes an inductor 32 and a capacitor 34, and removesa high frequency component from the output signal of the power switchingcircuit unit 250.

FIG. 7 is a waveform chart of a PWM signal output from the powerswitching circuit unit 250 according to an embodiment of the presentgeneral inventive concept.

Referring to FIG. 7, the power switching circuit unit 250 of FIG. 2increases an output from 1.2 W to 20 W when a supplied voltage V_(P)increases from 3 V to 12 V.

The general inventive concept can also be embodied as computer readablecodes on a computer readable recording medium. The computer readablerecording medium is any data storage device that can store data whichcan be thereafter read by a computer system. Examples of the computerreadable recording medium include read-only memory (ROM), random-accessmemory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical datastorage devices, and carrier waves (such as data transmission throughthe Internet). The computer readable recording medium can also bedistributed over network coupled computer systems so that the computerreadable code is stored and executed in a distributed fashion.

According to the present general inventive concept, since a variableDC-DC power supply to drive a switching power amplifier stage isseparately provided, it is possible to control a volume using a boostedvoltage and to improve an S/N ratio when an external power supply (e.g.,a battery charger) is installed. Also, since a loud speaker is drivenusing a high output voltage, it is possible to provide a user with anoptimal system. In addition, since the switching power amplifier stageis driven by a separate power supply other than an external powersupply, there is no influence of noises from an external power supply.Furthermore, it is possible to improve the S/N ratio by adaptivelycontrolling a volume using a variable power supply.

Although a few embodiments of the present general inventive concept havebeen shown and described, it will be appreciated by those skilled in theart that changes may be made in these embodiments without departing fromthe principles and spirit of the general inventive concept, the scope ofwhich is defined in the appended claims and their equivalents.

1. A mobile device comprising: a microcomputer unit to generate a volumevalue corresponding to a volume setting; a pulse width modulation (PWM)unit to modulate a digital audio signal into a PWM signal that has asmall output level; a variable power supply unit to detect aninstallation of an external power supply and to convert a voltage of aninternal power supply into a DC-DC voltage in a variable manner on thebasis of a voltage control value corresponding to the volume valuegenerated in the microcomputer unit; and a power switching circuit unitto perform switching power amplification on a PWM signal generated inthe pulse width modulation unit based on a voltage output from thevariable power supply unit.
 2. The mobile device of claim 1, wherein thevariable power supply unit includes: an internal power supply unit tosupply a power voltage charged with an external power supply; a volumecontrol unit to detect installation of the external power supply togenerate a voltage control value corresponding to a current volumelevel; and a DC-DC converter unit to convert a voltage of an internalpower supply unit into a DC-DC voltage in a variable manner on the basisof the voltage control value generated in the volume control unit. 3.The mobile device of claim 1, wherein the power switching circuit unitincludes switching elements to perform switching power amplification onthe PWM signal based on a voltage output from the DC-DC converter unit.4. A method of supplying a power voltage to a mobile device in avariable manner, the method comprising: modulating a digital audiosignal into a pulse width modulation (PWM) signal; detecting aninstallation of an external power supply; reading a volume value when itis detected that the external power supply is connected; generating avoltage control value corresponding to the volume value by comparing thevolume value with a reference value; performing a DC-DC conversion in avariable manner for a voltage supplied from an internal power supplyunit on the basis of the generated voltage control value; and performingpower switching on the PWM signal on the basis of the voltage controlvalue to control a signal output.
 5. The method of claim 4, whereinduring the generation of the voltage control value, a command is issuedto generate a voltage control value corresponding to the volume valuewhen the read volume value is higher than a reference value, andotherwise, to perform a conventional volume control.
 6. An apparatus tosupply a power voltage to a mobile device in a variable manner, theapparatus comprising: a pulse width modulator to modulate a digitalaudio signal into a pulse width modulation (PWM) signal; a sensor todetect whether an external power supply is installed; a microcomputer toread a volume value when the external power supply is detected; a volumecontrol unit to generate a voltage control value corresponding to thevolume value by comparing the volume value with a reference value; aDC-DC converter unit to perform a DC-DC conversion in a variable mannerfor a voltage supplied from an internal power supply unit on the basisof the generated voltage control value; and a power switching unit toperform power switching on the PWM signal on the basis of the generatedvoltage control value to control a signal output.